1. Field of Invention
Embodiments of the present invention relate to data processing systems. More particularly, embodiments of the present invention relate to methods and systems for obtaining data from legacy computer systems.
2. Background Information
Known data processing systems can include legacy computer systems that provide data through, for example, 3270 terminals. 3270 terminals are a class of terminals often used in the System Network Architecture (“SNA”) networks. SNA is a product of International Business Machines Corporation (“IBM”), headquartered in Armonk, N.Y. SNA is a structured architecture typically having a mainframe host computer acting as the network control center. The domain of an SNA network includes the host computer, front-end processors, cluster controllers, and terminals.
A 3270 terminal typically supports a display format defined by lines (i.e., rows) and columns. Examples of 3270 terminal display formats include 24 rows by 80 columns, 32 rows by 80 columns, 48 rows by 80 columns, 27 rows by 132 columns, and 25 rows by 160 columns. A 3270 terminal is an example of a dumb terminal because the 3270 terminal lacks substantial processing capabilities and is typically used for simple data entry and data retrieval tasks.
Known applications that send data to, and receive data from, legacy computer systems having 3270 terminals and the like typically identify data by, among other things, a display screen and a screen field having a position on the display screen. For example, a display screen may have a screen name, and a screen field having a position on the display screen can be identified, for example, by a row position, a column position, and a field length. Such legacy computer systems thereby identify data by screen location identifiers such as screen identifiers and screen position identifiers.
The format of the data sent to a 3270 terminal can dictate the display of data. The format (e.g., convention) has become known as a 3270 data stream, and a concept of a virtual screen is employed to facilitate the data exchange. Concepts of screen name, field name, and field data are preserved in the 3270 data stream, and a legacy computer can use the data stream for interactive screen sessions with users and -automated sessions with computers.
External computer systems can open a connection to a legacy computer system and simulate a screen-based session. The data exchange dialogue between a client system and the legacy computer system typically are based on conventions dictated by data location on a virtual screen. For example, it can be known that a name data value is on screen 2 at line 2 at column 25. The data may have a length of 40 characters. The client system can examine the data screen at those coordinates to retrieve the data value for the name. The physical device of a 3270 terminal need not be involved in the data transfer between computer systems. A physical device of a 3270 terminal was the origin of a data exchange protocol that has evolved, and references to a 3270 terminal encompass references to a virtual 3270 terminal having a 3270 data stream or a virtual screen.
The applications that send data to, and receive data from, these legacy computer systems are typically “hard coded” such that the code of the applications specifically refers to the screen name and screen position of data fields. When the layout of a 3270 screen is modified, the code of the applications must be updated, recompiled, re-tested, and re-released because the new screen names and screen positions of the data fields must be updated due to the new screen layout. In view of the foregoing, it can be appreciated that a substantial need exists for methods and systems that can advantageously obtain data from legacy computer systems.